Autopsy results from 44 people who died with COVID-19 show how the virus spreads not only through the respiratory system, but throughout the body, including the brain, persisting for months in some patients.
A description of the results published in the peer-reviewed journal Nature in Decemberunderscores how considerable the burden of infection can be, with viral fragments found in 79 of 85 body locations in the 44 patients.
The small study constitutes “the most comprehensive analysis to date of the cellular tropism, quantification and persistence of SARS-CoV-2 in the human body, including the brain”, according to its authors.
“Our results show that although the highest burden of SARS-CoV-2 is in respiratory tissues, the virus can spread throughout the body.”
The virus was able to spread to multiple organs and systems, even in patients who died within a week of their first symptoms, the researchers found.
The 44 people whose autopsies contributed to this research were all unvaccinated people who died of COVID-19. The median age of individuals was 62.5 years and 61.4% had three or more comorbidities. The median time from symptom onset to patient hospitalization was six days, with 18.5 days being the median time from symptom onset to death.
Overall, the autopsies showed that the virus was able to enter many body systems, although the researchers noted that there was a significantly higher load of SARS-CoV-2 RNA in the respiratory tissues. The researchers found that the virus had invaded more than 35 cell types and membranes in different body systems.
Of the 44 autopsies, 11 were whole-body and brain autopsies, providing the most complete picture of viral spread in these individuals.
Of these 11, the two with the shortest duration between symptom onset and death – four days and five days – had the highest amount of viral RNA in their respiratory system, with high levels also found in the cardiovascular system and optic tissue, among others. . .
SARS-CoV-2 was found in at least one central nervous system or brain tissue location in 10 of those 11 autopsies, including five out of six of those who died more than a month after first symptoms appeared .
The researchers noted that although there were significant viral traces found, the actual structural tissue of the brain was largely unaffected by the virus.
The individual who had the longest duration from symptom onset to death – 230 days – had been hospitalized multiple times and ultimately died of complications from a lung transplant, not COVID-19, but s tested positive for COVID-19 and showed viral traces in many parts of their body, including the respiratory system, heart, eye tissue and brain.
This indicates that the virus can persist in some patients’ bodies for months, the researchers noted.
The cause of death varied among individuals. Thirty-eight died from COVID-19, while six died from another basic condition while having COVID-19. Of those killed by the virus, 35 had either acute pneumonia or severe lung damage when they died.
Two of the patients included had only mild symptoms of COVID-19 and had died of other causes, but SARS-CoV-2 RNA was found to be spreading widely throughout their bodies, suggesting that Although the bulk of autopsies have focused on severe and fatal cases, the virus can penetrate far into the body even in mild cases.
The study is limited by its small scope and focuses on unvaccinated older people who died with COVID-19, meaning these results may not reflect what happens when younger, vaccinated people get the virus.
Previous autopsy research has found evidence of COVID-19 in multiple systems, but some have speculated that viral traces found outside the respiratory system could be due to residual blood left in tissues or a cross contamination. The researchers say that is not the case in this new study, which confirmed SARS-CoV-2 at the cellular level.
Another aspect that interested the researchers was how long the virus persisted in the tissues. They found that among those who had a longer interval between symptom onset and death, the difference between the level of virus in respiratory and non-respiratory tissues decreased significantly. This may be because different fabrics are better at fighting off the virus and identifying it, the researchers speculated.
“Understanding the mechanisms by which SARS-CoV-2 evades immune detection is essential to guide future therapeutic approaches to facilitate viral clearance,” the authors said.
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